Chapter 54: Review Of The Immune System

Question 1

2 types of immune responses

Answer 1

Natural immunity and acquired immunity

Question 2

Natural immunity (innate)

Answer 2

At location

Respond immediately, generalized
Inflammation response and recruiting cells that phagocytize pathogens

Chemical barriers
HCl (stomach), Lysosome (sweat, tears), lactic acid (vagina)

Physical barriers
Skin, mucosa (resp. GI, GU)

Question 3

Initial immune response

Answer 3

Macrophages recognize pathogen and activate innate system

Dendritic cells pick up antigens and track down T and B cells, activate specific system

Invading pathogen activates the complement system via lectin pathway or alternative pathway

Release cytokines (signalling proteins) to receive help and alert infection -> inflammation. Cytokines recruit more macrophages, monocytes, neutrophils. Inflammation also causes vasodilation, increase vas permeability, mast cell degranulation, activation of clotting system, and activation of kinin system. Inflammation also causes neutrophils and macrophages to release more cytokines called interleukins. This is known was the acute phase response -> systemic inflammatory response -> release more cytokines -> interleukin 1 to the brain to signal fever, decrease appetite, and lethargy. Interleukin 6 -> liver to produce acute phase proteins (opsonins). IL-8 recruits and activates more neutrophils. IL-2 and IL-12 activate NK cells. TNF-alpha is release and dose all of these effects by itself

Question 4

Phagocytosis

Answer 4

destroy pathogens after they are recognized. Wrap cell membrane around pathogen and absorb them in cell. Destroy pathogen using enzymes and turning them into harmless waste products

Question 5

Opsonins

Answer 5

complex molecules that attach to pathogens and make it easier for macrophages and neutrophils to recognize and phagocytize that pathogen. Ex. CRP produced by liver by IL-6. measure CRP in pt to see how much inflammation is in the body. Great indicator of level of infection.

Question 6

Specific acquired immunity

Answer 6

Away from infection

Specialized, takes longer to respond

Cell-mediated
T cells

Antibody-mediated: Humoral
B cells

T and B cells are lymphocytes and free to roam in blood and lymphatic system. Spend most time in lymph node and mucosa associated lymphoid tissue

Question 7

Complement system

Answer 7

Complement system works alongside the innate and specific immune system

Helps them destroy pathogens

Complement proteins C1-C9

Once system is activated, proteins activate each other thru complement cascade

Results in opsonins, inflammation, destroy pathogens

Triggered directly by pathogens (lectin and alt. pathway) and classical (AB-AG complexes)

Question 8

B lymphocytes

Answer 8

Make Ab

B cells have AB on cell membrane that are specific to single antigen

Plasma cells are B cells that have differentiated and become AB producing cells

Question 9

Cytolytic T lymphocytes

Answer 9

Cytolytic T cells, CD8 cells

Do not produce antibodies

Attack and kill target cells directly

Each t cell has t cell receptors that are specific to single antigen

Question 10

Dendritic cells

Answer 10

Dentrictic cells are messengers that pick up antigen and display them on cell surface (HLA class 2 moelcules) and bring them into lymph system. When a b or t cell recognize pathogen, they become activated. Start the specific immune response.

Question 11

Helper t lymphocytes

Answer 11

Helper T cells, CD4 cells
Antibody production by B cells
Required for an effective immune response

Activation of cytolytic T cells
Promote type IV sensitivity reactions, also known as delayed-type hypersensitivity (DTH)

Question 12

Specific immune response

Answer 12

Present to CD4 t cell then proliferation to TH cells -> release cytokines to present molecule on HLA class 1 molecule so they can be recognized by CD8 t cell -> differ into cytotoxic t cell

TH cells also release cytokines for C B cells -> plasma cells –> AB and memory B cells for immune memory

TH cells also travel to site of infection to release cytokines to recruit macrophages and macrophages to site of infection -> phagocytosis and inflammation

TC cells destroy virally infected cell by attaching themselves to HLA class 1 molecule antigen 2 ways -> 1. Granule exocytosis. Spray infected cell with enzymes -> cell lysis. 2. FAS molecule activation. “Self destruct switch” once activated, it causes cell to undergo apoptosis

Plasma cells are B cells that have differentiated and become AB producing cells

Question 13

Macrophages

Answer 13

Begin in bone marrow, enter blood as monocytes, and infiltrate tissues, where they evolve into macrophages

Principal scavengers of the body
Recognize pathogens via pathogen associated molecular patterns using receptors (toll-like receptors)

Specific acquired immunity
Activation of T cells
Final mediators of DTH
Phagocytize cells tagged with antibodies

Also play key roles in natural immunity and inflammation

Question 14

Mast cells and basophils

Answer 14

Mediate immediate hypersensitivity reactions

Release histamine, heparin, and other compounds that cause s/sx of immediate hypersensitivity

Mast cells are located in skin and others soft tissues

Basophils are in the blood

Question 15

Neutrophils

Answer 15

Polymorphonuclear leukocytes (PMNs)
Phagocytize bacteria and other foreign particles

Question 16

Eosinophils

Answer 16

Attack and destroy foreign particles that have been coated with antibodies of the immunoglobulin (Ig) E class

Question 17

Antibodies

Answer 17

Alternative names
Immunoglobulins
Gamma globulins

Family of structurally related glycoproteins

Mediate humoral immunity

Recognize and bind with specific antigens

Produced by B lymphocytes

Five classes of antibodies:
IgA, IgD, IgE, IgG, and IgM

Y shaped

Top is variable region that matches different Ag

Bottom is fixed shape and recognized by many cells of immune system

Help immune system:
Attach to toxins (Ag) and neutralize them
Attach to receptors of viruses and bacteria and prevent them from carrying out their function
Agglutination
Opsonins that are highly specific to invading pathogen

Question 18

Antigens

Answer 18

Molecules that induce specific immune responses

May trigger production of antibodies or cytotoxic T cells, or both

Antibodies recognize and bind selected small portions of the antigen

More than one antibody can bind to the antigen

Question 19

Characteristic Features of the Specific Immune Response

Answer 19

Specificity
Immune responses are triggered by specific antigens

Diversity
Millions of different antigenic determinants

Memory
Exposure to an antigen affects the immune system such that reexposure produces a faster, greater, and more prolonged response

Time limitation
Immune responses only last while there is stimulus

Selectivity for antigens of nonself origin
Targets only foreign antigens (normal conditions)

Question 20

Phases of immune response

Answer 20

Recognition phase
Antigen recognition by B cells and T cells

Activation phase
Proliferation
Differentiation of activated lymphocytes

Effector phase
Elimination of antigen

Question 21

Major Histocompatibility Complex Molecules

Answer 21

Group of genes that codes for major histocompatibility complex (MHC) molecules

MHC molecules become expressed on the surface of all cells

Play a key role in the activation of helper and cytotoxic T lymphocytes

Guide cytotoxic T lymphocytes toward target cells

Provide the basis for distinguishing between self and nonself

Question 22

Class I MHC molecules

Answer 22

Found on virtually all cells except erythrocytes

Located on the surface of antigen-presenting cells (APCs)

Help initiate immune responses by “presenting” antigen to cytotoxic T cells

Question 23

Class II MHC molecules

Answer 23

Found primarily on B cells and APCs (macrophages and dendritic cells)

Located on the surface of APCs

Help initiate immune responses by presenting antigen to helper T cells

Question 24

Cytokine

Answer 24

Any mediator molecule (other than an antibody) released by any immune system cell

Question 25

Lymphokine

Answer 25

Cytokine released by a lymphocyte

Question 26

Monokine

Answer 26

Cytokine released by a mononuclear phagocyte (monocyte or macrophage)

Question 27

Antibody-Mediated (Humoral) Immunity

Answer 27

Production of antibodies
Interaction of three types of cells:

B cells
Make antibodies

Helper T cells (CD4 cells)
Stimulate B cells

Antigen-presenting cells (macrophage or dendritic)
Activate CD4 cells

Antibody effector mechanisms

Opsonization of bacteria

Activation of the complement system

Neutralization of viruses and bacterial toxins

Question 28

Type IV Hypersensitivity (Cell-Mediated Immunity)

Answer 28

Delayed-type hypersensitivity
Activation of helper T cells
Activation of macrophages

Cytolytic T lymphocytes (CTLs, CD8 cells)
Activation of cytolytic T cells
Recognition of virally infected target cells
Mechanism of cell kill
Binding of a CTL to its target cell
Release of mediators that kill the target
Cause target-cell lysis